The present invention relates to a piston for an internal combustion engine and more specifically to a piston having therein a cooling channel formed in a piston crown and arranged to convey a cooling oil.
A patent document 1 (JP2009-221900A) and a patent document 2 (JP2009-281387A) show pistons for internal combustion engines of motor vehicles.
A piston disclosed in the patent document 1 includes an annular cooling channel formed in the piston crown and arranged to covey the cooling oil. The cooling oil injected from an oil jet provided in a lower portion of the cylinder bore is introduced into the cooling channel, and caused to flow in the piston crown to cool the piston crown and piston rings fit in three piston ring grooves formed in the outside circumferential surface of the piston crown.
A piston disclosed in the patent document 2 includes a plurality of drain holes formed in the piston crown so as to extend radially in the piston crown from an oil ring groove to the inside space of the piston and arranged to drain the oil scraped by a piston ring from the inside circumferential wall surface of the cylinder bore, from the piston groove to the inside space of the piston through the drain holes.